This invention relates to a dial-type combination lock.
As is known, wide acceptance have gained, in the field of safety locks, combination locks which comprise, as the basic components thereof, combination dials or disks formed with edge seats or "gates", a driver element operable from the outside, e.g through an indexed knob, and arranged to act on said dials and provided with a drive seat located at its periphery, and a stud mounted on a bolt element of the lock. Said stud is adapted to engage with all of said seats when the latter are brought into mutual alignment, that is, when the driver element, operatively connected to said dials, is turned from the outside into a set combination.
It is current practice in the art to make the stud with a barb-like shape having a hooked end which can be inserted into the drive seat of the driver element and the opposite end articulated, through a swivel connection, on said bolt element. This prior stud configuration is further provided with a lug adapted for insertion into said edge seats on the combination dials. When the latter have their respective edge seats aligned to one another, said lug moves into the seats and the stud is allowed to rotate about said swivel connection and engage with the driver element through its hooked end. Thus, the driver element is made operatively rigid with the bolt element and can move it to open a door or the like.
The combination dials are currently formed by rings engaging, by means of specially provided internal grippers, with peripherally toothed hubs. The rings are formed peripherally with the cited "gates" or edge seats, the hubs having guide projections adapted to operatively connect each combination dial to adjacent dials and said driver element. The angular offset of the edge seats from the guide projections determines the combination numbers to be set in order to align said edge seats and enable said stud to "hook up" said driver element to connect it to said bolt element.
Prior locks, as outlined above, have been used for years and always developed some faults, which could not be remedied heretofore.
The first of such faults in the following. Each thrust exerted on the bolt element reflects on the stud, and the stud, when loaded, is frictionally jammed against the adjacent elements. Thus, the lock will not open with the bolt element thus loaded and fail to directly entrain the closure elements of a door or the like whereto it is connected, since this action would in all cases involve application of a load. This situation is aggravated by another fault of such prior locks: the travel distance of the bolt element is invariably quite limited, and hence, only suitable for "locking" and not direct "dragging" locks.
It should be further noted that the barbed stud enters said edge seats or "gates" along a path on an arc of a circle with its pivot point on said swivel connection. This path form requires that considerable play be allowed betfween the stud and edge seats, and this play permits the lock to be opened even with different combinations from the set one, so long as they happen to be proximate to it.
This inaccuracy adds to the particularly serious one originating from that, in the combination dials, the rings are made rigid with the respective hubs through tooth formations. The net result is that the change in the angular positions, between hubs and rings, cannot be set continuously but made dependent on the tooth pitch.
Finally, it is well known in the art that if in such prior locks the drive seat happens to be in the aligned position with the combination dial edge seats immediately after the last combination number has been dialled--which number is always dialled by rotation in a counterclockwise direction--the lock jams. This because the stud enters said seats when the active thrust portion of said drive seat is a bevelled side: the stud is then urged directly by the combination dials rather than by the driver element. To prevent this occurrence, instructions for use invariably warn of not using for the last combination number a given series of numbers which produce the above-described condition. However, it is not infrequent for the user to make a mistake, and the lock jams up.